[LEDE-DEV] [PATCH v1 1/1] openssh: disable passwords for openssh server

[Stijn Segers]

Yousong Zhou <yszhou4tech at gmail.com> schreef op 14 februari 2018 09:06:11 CET:
>On 14 February 2018 at 11:53, Philip Prindeville
><philipp_subx at redfish-solutions.com> wrote:
>>
>>> On Feb 11, 2018, at 3:54 AM, Yousong Zhou <yszhou4tech at gmail.com>
>wrote:
>>>
>>> On 9 February 2018 at 08:28, Philip Prindeville
>>> <philipp at redfish-solutions.com> wrote:
>>>> From: Philip Prindeville <philipp at redfish-solutions.com>
>>>>
>>>> Allowing password logins leaves you vulnerable to dictionary
>>>> attacks.  We disable password-based authentication, limiting
>>>> authentication to keys only which are more secure.
>>>>
>>>> Note: You'll need to pre-populate your image with some initial
>>>> keys. To do this:
>>>>
>>>> 1. Create the appropriate directory as "mkdir -p files/root/.ssh"
>>>>   from your top-level directory;
>>>> 2. Copy your "~/.ssh/id_rsa.pub" (or as appropriate) into
>>>>   "files/root/.ssh/authorized_keys" and indeed, you can collect
>>>>   keys from several sources this way by concatenating them;
>>>> 3. Set the permissions on "authorized_keys" to 644 or 640.
>>>>
>>>
>>> If forgetting doing this means I may need physical connection like
>vga
>>> monitor or serial connection to "unlock" the device, very likely I
>>> will hate this security enforcement...  It's just the inconvenience
>>> regardless of whether the said situation should happen.  As a user
>I'd
>>> like to keep this level of convenience as using password
>>> authentication and turn it off when I see it appropriate.
>>>
>>>                yousong
>>>
>>
>>
>> Well, we’re at an impasse because some people have said “this should
>be the new norm and it’s a mistake not to disable it unconditionally”
>and others have said the opposite, “yes, okay, let’s do this but only
>as an option”.
>>
>> So I’m happy to go other way but we should reach a consensus.
>>
>> What if it *is* an option but depends on a virtual package that takes
>a value (like CONFIG_SSH_PUBLIC_KEYS) and squirts that into the
>/root/.ssh/authorized_keys file.
>>
>> Would that work for everyone?
>>
>> You could still lock yourself out of a box by (a) mis-formatting the
>keys or (b) getting the wrong public keys that don’t match your
>installed private keys, but getting this to be absolutely foolproof is
>a fool's errand.
>>
>> So what constitutes “good enough”?
>>
>> -Philip
>>
>
>No, it's just complicating things up.  When people really cares about
>the default settings' security, the will override the default by also
>specifying files/etc/ssh/sshd_config besides
>files/root/.ssh/authorized_keys.  No need to pass on such complexity
>as virtual packages and another config options for others.
>
>                yousong
>

This only applies to OpenSSH, not Dropbear right? So this won't affect stock images?

We should consider people rolling their own and using OpenSSH by default. This might be a nasty surprise - flash, reboot, realise you're locked out.

SSH access from WAN is disabled by default anyway, as is access to the web interface. We already switched from telnet to SSH for initial login. I don't see any gaping security holes... 

On top of that, the project having a DIY spirit, if people start tinkering with SSH, they should know what they're doing. Just like when they start using LEDE/OpenWrt.

My 2 cents

Stijn


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